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101.
Sergei Popov David Blaschke Hovik Grigorian Mikhail Prokhorov 《Astrophysics and Space Science》2007,308(1-4):381-385
We discuss three topics related to the neutron star (NS) mass spectrum. At first we discuss the possibility to form low-mass
(M≲1M
⊙) objects. In our opinion this and suggest this is possible only due to fragmentation of rapidly rotating proto-NSs. Such
low-mass NSs should have very high spatial velocities which could allow identification. A critical assessment of this scenario
is given. However, the mechanism has its own problems, and so formation of such objects is not very probable. Secondly, we
discuss mass growth due to accretion for NSs in close binary systems. With the help of numerical population synthesis calculations
we derive the mass spectrum of massive (M>1.8M
⊙) NSs. Finally, we discuss the role of the mass spectrum in population studies of young cooling NSs. We formulate a kind of
mass constraint which can be helpful, in our opinion, in discussing different competitive models of the thermal evolution of NSs.
S.B.P. wants to thank the Organizers for support and hospitality. The work of S.B.P. was supported by the RFBR grant 06-02-16025
and by the “Dynasty” Foundation (Russia). The work of M.E.P.—by the RFBR grant 04-02-16720 and that of H.G. by DFG grant 436
ARM 17/4/05. 相似文献
102.
103.
Sergei M. Poleshchikov 《Celestial Mechanics and Dynamical Astronomy》2003,85(4):341-393
The sets of L-matrices of the second, fourth and eighth orders are constructed axiomatically. The defining relations are taken from the regularization of motion equations for Keplerian problem. In particular, the Levi-Civita matrix and KS-matrix are L-matrices of second and fourth order, respectively. A theorem on the ranks of L-transformations of different orders is proved. The notion of L-similarity transformation is introduced, certain sets of L-matrices are constructed, and their classification is given. An application of fourth order L-matrices for N-body problem regularization is given. A method of correction for regular coordinates in the Runge–Kutta–Fehlberg integration method for regular motion equations of a perturbed two-body problem is suggested. Comparison is given for the results of numerical integration in the problem of defining the orbit of a satellite, with and without the above correction method. The comparison is carried out with respect to the number of calls to the subroutine evaluating the perturbational accelerations vector. The results of integration using the correction turn out to be in a favorable position. 相似文献
104.
Sergei I. Ipatov 《Meteoritics & planetary science》2023,58(6):752-774
The estimates of the delivery of icy planetesimals from the feeding zone of Proxima Centauri c (with mass equal to 7mE, mE is the mass of the Earth) to inner planets b and d were made. They included the studies of the total mass of planetesimals in the feeding zone of planet c and the probabilities of collisions of such planetesimals with inner planets. This total mass could be about 10–15mE. It was estimated based on studies of the ratio of the mass of planetesimals ejected into hyperbolic orbits to the mass of planetesimals collided with forming planet c. At integration of the motion of planetesimals, the gravitational influence of planets c and b and the star was taken into account. In most series of calculations, planetesimals collided with planets were excluded from integrations. Based on estimates of the mass of planetesimals ejected into hyperbolic orbits, it was concluded that during the growth of the mass of planet c the semi-major axis of its orbit could decrease by at least a factor of 1.5. Depending on possible gravitational scattering due to mutual encounters of planetesimals, the total mass of material delivered by planetesimals from the feeding zone of planet c to planet b was estimated to be between 0.002mE and 0.015mE. Probably, the amount of water delivered to Proxima Centauri b exceeded the mass of water in Earth's oceans. The amount of material delivered to planet d could be a little less than that delivered to planet b. 相似文献
105.
The paper presents some methods of numerical modeling and a study of moisture changing in frozen clay soils considering rates of freezing in the base of construction.An impact assessment of moisture changes in clay soils affecting strength characteristics during thawing was carried out in stability tests. 相似文献
106.
Schubert H Feuerpfeil P Marquardt R Telesh I Skarlato S 《Marine pollution bulletin》2011,62(9):1948-1956
Remane’s species-minimum concept, which states that the lowest number of taxa occurs at the horohalinicum (5-8 psu), was tested by investigating macroalgal diversity on hard substrates along the natural salinity gradient in the Baltic Sea. Field data on species occurrence and abundance were collected by SCUBA diving along 10 transects of the Finnish, Swedish and German coasts, covering a salinity range from 3.9 to 27 psu. Macroalgal species numbers declined steadily with salinity, decreasing until 7.2 psu was reached, but in the horohalinicum, a marked reduction of species number and a change in diversity were indicated by the Shannon index and evenness values. The non-linear decrease in macroalgal diversity at 5-8 psu and the lack of increase in species numbers at salinities below 5 psu imply a restricted applicability of Remane’s species-minimum concept to macroalgae. 相似文献
107.
108.
Carmen Gaina Sergei Medvedev Trond H. Torsvik Ivan Koulakov Stephanie C. Werner 《Surveys in Geophysics》2014,35(5):1095-1122
Knowledge about the Arctic tectonic structure has changed in the last decade as a large number of new datasets have been collected and systematized. Here, we review the most updated, publicly available Circum-Arctic digital compilations of magnetic and gravity data together with new models of the Arctic’s crust. Available tomographic models have also been scrutinized and evaluated for their potential to reveal the deeper structure of the Arctic region. Although the age and opening mechanisms of the Amerasia Basin are still difficult to establish in detail, interpreted subducted slabs that reside in the High Arctic’s lower mantle point to one or two episodes of subduction that consumed crust of possibly Late Cretaceous–Jurassic age. The origin of major igneous activity during the Cretaceous in the central Arctic (the Alpha–Mendeleev Ridge) and in the proximity of rifted margins (the so-called High Arctic Large Igneous Province—HALIP) is still debated. Models of global plate circuits and the connection with the deep mantle are used here to re-evaluate a possible link between Arctic volcanism and mantle plumes. 相似文献
109.
Thierry Appourchaux Raymond Burston Yanbei Chen Michael Cruise Hansjörg Dittus Bernard Foulon Patrick Gill Laurent Gizon Hugh Klein Sergei Klioner Sergei Kopeikin Hans Krüger Claus Lämmerzahl Alberto Lobo Xinlian Luo Helen Margolis Wei-Tou Ni Antonio Pulido Patón Qiuhe Peng Achim Peters Ernst Rasel Albrecht Rüdiger Étienne Samain Hanns Selig Diana Shaul Timothy Sumner Stephan Theil Pierre Touboul Slava Turyshev Haitao Wang Li Wang Linqing Wen Andreas Wicht Ji Wu Xiaomin Zhang Cheng Zhao 《Experimental Astronomy》2009,23(2):491-527
ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test general relativity with
an improvement in sensitivity of over three orders of magnitude, improving our understanding of gravity and aiding the development
of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and
our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude
improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is an
international project, with major contributions from Europe and China and is envisaged as the first in a series of ASTROD
missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way,
two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth,
to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II) is envisaged as a three-spacecraft mission which would
test General Relativity to 1 ppb, enable detection of solar g-modes, measure the solar Lense–Thirring effect to 10 ppm, and
probe gravitational waves at frequencies below the LISA bandwidth. In the third phase (ASTROD III or Super-ASTROD), larger
orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below
the ASTROD II bandwidth.
相似文献
Wei-Tou NiEmail: |
110.
Sergei Nayakshin Seung-Hoon Cha Alexander Hobbs 《Monthly notices of the Royal Astronomical Society》2009,397(3):1314-1325
We present a new framework for radiation hydrodynamics simulations. Gas dynamics is modelled by smoothed particle hydrodynamics (SPH), whereas radiation transfer is simulated via a time-dependent Monte Carlo approach that traces photon packets. As a first step in the development of the method, in this paper we consider the momentum transfer between radiation field and gas, which is important for systems where radiation pressure is high. There is no fundamental limitation on the number of radiation sources, the geometry or the optical depth of the problems that can be studied with the method. However, as expected for any Monte Carlo transfer scheme, stochastic noise presents a serious limitation. We present a number of tests that show that the errors of the method can be estimated accurately by considering Poisson noise fluctuations in the number of photon packets that SPH particles interact with per dynamical time. It is found that, for a reasonable accuracy, the momentum carried by photon packets must be much smaller than the typical momentum of SPH particles. We discuss numerical limitations of the code, and future steps that can be taken to improve performance and applicability of the method. 相似文献